Traditionally, closed form or hydroforming techniques are used to draw and shape metal tubes. Conventional hydroforming techniques often involve two steps: (1) placing the desired bends in the tube and (2) forming the tube to the desired configuration. The second step of this process usually requires placing a tubular member having an open bore in a mold and pinching off the ends of the tube. A pressurized liquid is then injected into the open bore, causing the tube to stretch and expand out against the mold.
The manufacturing advantages of the hydroforming process is that it allows formation of relatively long tubular structures having a seamless perimeter. This process eliminates the cost of welding, machining, or fastening operations often used to shape the part in the desired configuration. As a result, a hydroform or closed form structure very often has a high length to diameter ratio. For instance, a hydroform structure may have a length in excess of 15′ and a diameter ranging from approximately ¾″ to more than 12″. To this end, a further manufacturing process advantage of a hydroform structure is that it can exceed the length of other tubular members, such as torsion bars or tubular bars, formed using other processes.
Additionally, hydroforming processing creates complex structural shapes that typically include bends and contour changes. Often the number of bends and contour changes in a hydroformed bar are greater and more complex than those found in torsion bars or other tubular structures formed using different techniques. These shapes often have particular application in land transportation vehicles which require contour changes to reflect vehicle styling and traditional automotive architecture in the form of automotive rails, pillars, and other structural members.
In addition, hydroform structures typically have a constant wall thickness prior to forming, and might develop strength differences at the site of bends or changes in contour, as well as at certain locations along a long tubular section. Thus, it is often desirable to reinforce closed form and hydroform sections to improve their structural stiffness, strength, and durability, particularly in automotive vehicle applications.
Traditional ways of reinforcing tubular structures such as hydroforms and other closed forms include sliding a metal sleeve inside the tube and welding the reinforcing member in place. However, because the hydroform often includes one or more shapes or bends, or one or more changes in contour and/or diameter, it is often difficult to insert the sleeve into the hydroform at the precise location of the weak portion. Other techniques include reinforcing the hydroform from the outside by welding the sleeve onto the outside of the hydroform. However, hydroforms are often used in applications having very close tolerances, resulting in little or no clearance for an externally placed reinforcing member. Accordingly, exterior reinforcements are often not as effective as interior reinforcements.
Additionally, in many operations the weight of the tubular member is critical and must be kept low as possible. Thus, the use of an external sleeve adds unwanted weight to the tubular assembly. Still further, the welding operation tends to be labor intensive during the manufacturing process, time consuming and inexact, increasing the cost of forming the hydroform member and producing parts that have questionable reliability. Finally, these additional manufacturing steps and operations are often cumbersome and difficult to integrate into a final vehicle manufacturing process in that additional tooling would need to be developed by the manufacturer and assembly plant resources, labor, maintenance, and space would need to be dedicated and expensed by the vehicle manufacturer.
Accordingly, there is a need in industry and manufacturing operations for system, device, and method for reinforcing the weak areas of closed forms and other hydroform tubes, such as a hydroform rail, without significantly increasing the weight and manufacturing complexity. In particular, there is a need for reinforcing a closed form or hydroform, which utilizes a plurality of segments or portions to achieve integrated reinforcement within the closed form since the contour or shape of typical tubes do not allow for placement of single piece reinforcement members. In this regard, the present invention addresses and overcomes the shortcomings found in the prior art by providing a multi-segment reinforcement system having at least two segments or portions capable of being modularly attached or otherwise engaged in segments within a hydroform that may then be fixed in location through the use of a third segment or portion which serves as a locking, positioning, and retaining member of the reinforcement system within the hydroform or other closed form. However, the plurality of modularly attached segments could also be locked, positioned, and retained within a hydroform through the use of retention means, such as a string, wire, or chain looped through each of the segments which provides enough tension to retain each of the segments in a desired position while the entire system (i.e. the segments with an amount of bonding material disposed along at least a portion of each of the segments) is exposed and cured by the heat typically encountered in an automotive painting operation. Structural reinforcement of the hydroform is achieved through activation by heat of the bonding material disposed along at least a portion of an outer or exterior surface of the plurality of segments or portions, such a material would typically expand when exposed to heat or other energy source and in doing so structurally adhere the segments or portions to each other and the hydroform. Further, it is contemplated that the system would have greater flexibility to a range of applications by allowing each segment or portion of the plurality of segments to also have the capability of receiving a suitable amount of sealing material, sound absorption material, and/or an expandable material, or a combination thereof.